>> GOOD AFTERNOON, EVERYBODY. THE WENTHOLD MEMORIAL LECTURE BEGAN SIX YEARS AGO TO HONOR THE MEMORY OF OUR FRIEND AND COLLEAGUE ROBERT WENTHOLD WHO SERVED AS NIDCD SCIENTIFIC DIRECTOR FROM 1998-2008. TODAY WE'RE CELEBRATING BOB'S REMARKABLE CONTRIBUTIONS TO NIH WITH A LECTURE ENTITLED "HOW COCHLEAR NUCLEAR NEURONS ENABLE MAMMALS TO HEAR," AND THIS LECTURE WILL BE DELIVERED BY DONATA OERTEL, WHO IS A LONGTIME FRIEND OF BOB WENTHOLD'S. I'D LIKE TO THANK CHRIS WENTHOLD AND HER FAMILY FOR JOINING US FOR THIS LECTURE TODAY. DR. OERTEL IS A PROFESSOR AND RECIPIENT OF THE 2015 MARY HERMAN AND LUCY RUBINSTEIN CHAIR OF NEUROSCIENCE TESTIFY UNIVERSITY OF WISCONSIN SCHOOL OF PUBLIC HEALTH IN MADISON. AT THE CONCLUSION OF THE LECTURE WE WOULD LIKE TO INVITE YOU TO JOIN US FOR A LIGHT RECEPTION, AND I WANT TO TAKE THIS OPPORTUNITY TO THANK THE FOUNDATION FOR ADVANCE THE EDUCATION IN SCIENCES FOR THEIR GENEROUS SUPPORT OF THIS RECEPTION. AND WITH THAT, I'D LIKE TO ASK DONATA TO COME UP TO THE PODIUM AND I'M LOOKING FORWARD TO HEARING WHAT SHE HAS TO SAY. [APPLAUSE] >> THANK YOU SO VERY MUCH FOR BEING HERE. BOB WENTHOLD WAS A VERY FINE SCIENTIST, AND ACTUALLY HE WAS A RALLY WONDERFUL PERSON TOO. HE WAS KIND AND GENEROUS AND JUST IMMENSELY DECENT. AND I THINK MANY OF YOU HERE FEEL AS I DO THAT HE LEFT US MUCH TOO SOON, AND PROBABLY MANY OF YOU, LIKE I, MISS HIM. SO MY VERY HIGH REGARDS FOR BOB MAKES THIS INVITATION A REALLY SPECIAL ONE, ONE THAT I FEEL TREMENDOUSLY HONORED ABOUT. SO BOB AND I SHARED A LOT. WE COMPETED FOR TWO JOBS. HE GOT BOTH OF THEM AND I ONLY GOT ONE. [LAUGHTER] AND THAT DESERVES A LITTLE EXPLANATION. SO HE AND I BOTH APPLIED FOR A JOB IN THE DEPARTMENT OF NEUROPHYSIOLOGY IN 1981, AND JOE HIND, WHO WAS THE SHARE OF THE DEPARTMENT AT THE TIME, ENDED UP GOING TO THE DEAN AND PERSUADING HIM TO HIRE BOTH BOB WENTHOLD AND ME. AND SO BOB AND I STARTED OUR CAREERS AS ASSISTANT PROFESSORS TOGETHER AT THE UNIVERSITY OF WISCONSIN. ANOTHER THING THAT WE HAD IN COMMON IS THAT BOTH OF US HAVE BATTLED CANCER. AND A THIRD THING THAT WE HAVE IN COMMON IS THAT WE ARE INTENSELY INTERESTED IN THE AUDITORY SYSTEM AND IN IN THE AUDITORY PATHWAY WHICH IS THE COCHLEAR NUCLEAR COMPLEX. AND SO THOSE OF YOU WHO DON'T KNOW WHERE THAT IS, LET ME SHOW YOU. SO THIS IS THE SIDE VIEW OF A MOUSE, IN WHICH I'VE CUT AWAY THE CEREBRAL HEMISPHERE AND THE CEREBELLUM. AND YOU CAN SEE HOW THE AUDITORY NERVE CARRIES INFORMATION FROM THE COCHLEA, RIGHT HERE I HAD TO CUT THAT OFF. IT CARRIES INFORMATION TO THE VENTRAL AND DORSAL COCHLEA ON THE BRAIN THEM. THE VENTRICAL AND DORSAL ARE DIFFERENT. I CAN'T SUMMARIZE BOB'S WORK, SO I WANTED TO TELL BUT SOME OF HIS PAPERS WHICH ARE MY FAVORITE, AND WHICH ARE ALSO PAPERS ON WHICH WE WERE ABLE TO BUILD. SO WHEN BOB INTERVIEWED FOR THE POSITION AT THE UNIVERSITY OF WISCONSIN, HE HAD DONE A BODY OF WORK THAT WAS ASSOCIATED WITH TRYING TO FIGURE OUT WHAT THE NEUROTRANSMITTER IS OF THE AUDITORY NERVE. AND I DON'T KNOW IF YOU GUYS REMEMBER THIS FROM YOUR OLD NEUROSCIENCE COURSES, BUT IT'S GENERALLY ACCEPTED THAT THERE ARE CRITERIA ONE HAS TO MEET BEFORE YOU IDENTIFY SOMETHING AS A NEUROTRANSMITTER OF ANYTHING. SO YOU HAVE TO SHOW THAT ITS SYNTHESIZED AND STORED PRESYNAPTICALLY, RELEASED FROM THE TERMINALS, IF YOU APPLY EXTRINSICALLY YOU SHOULD MIMIC SYNAPTIC RESPONSE. BOB HAD DONE SOME LOVELILY PAPERS. THIS IS BEFORE IMPACT FACTORS, AND IMPORTANT PAPERS WERE PUBLISHED IN MANY DIFFERENT JOURNALS. SO HE SHOWED THAT ASPARTIC ACED AND GLUTAMATE LEVELS CHANGED, IF YOU CUT THE AUDITORY NERVES AND LET FIBER DEGENERATE, PART OF WHAT SHOWS IT'S STORED PRESYNAPTICALLY, WITH THE DECREASE AFTER LESION OF AUDITORY NERVE SHOWING IT WAS SYNTHESIZED AND SHOW THAT IT WAS RELEASED, IF YOU TOOK COCHLEAR NUCLEAR TISSUE AND PUT IT, DEPOLARIZED IT WITH POTASSIUM, THAT GLUTAMATE WAS RELEASED. SO NOTICE THESE ARE 1979, 1980, 1977, SO THAT WAS ALL DONE BEFORE HE CAME TO WISCONSIN. SO WHEN I WAS HIRED, I WAS TRYING TO GET SLICES OF THE COCHLEAR NUCLEI TO BE FUNCTIONAL, AND SO I THOUGHT ONE OF THE EXPERIMENTS THAT I SHOULD DO EARLY ON IS TO LOOK AT THIS FINAL CRITERION. SO WE HAVE LEARNED HOW TO MAKE RECORDINGS FROM SLICES. WE HAVE LEARNED HOW TO IDENTIFY WHICH CELLS WERE WHICH ON THE BASIS OF THEIR ELECTROPHYSIOLOGICAL CHARACTERISTICS. SO I MADE RECORDINGS FROM BUSHY CELLS, CELLS KNOWN TO RECEIVE VERY LARGE BEAUTIFUL ENDINGS LOOKED TO SEE WHETHER THESE CELLS WERE SENSITIVE TO GLUTAMATE AS I EXPECTED THEY WOULD BE. AND HERE IS WHAT I FOUND. SO HERE YOU SEE SIX DIFFERENT PANELS, AND EACH PANEL TWO SUPERIMPOSED TRACES. IN ONE TRACE I INJECTED DEPOLARIZING CURRENT WHICH PRODUCED AN ACTION POTENTIAL, AND AS IS CHARACTERISTICS FOR BUSHY CELLS FIRING IS TRANSIENT. THE NEXT TRACE I INJECT HYPER POLARIZING CURRENT WHICH SHOWS WHAT TIME CONSTANT AND INPUT RESISTANCE OF THAT CELL. AS IS CHARACTERISTIC OF THESE CELLS, THEY OFTEN FIRE ANODE BREAK ACTION POTENTIAL. AND THEN IN THE LATTER PART OF THE TRACE, I GAVE A SHOCK TO THE AUDITORY NERVE AND HERE YOU CAN SEE THE SUPER THRESHOLD SYNAPTIC RESPONSE. TO MAKE SURE THAT SOLUTIONS WERE BEING EXCHANGED, I PUT ON A PHYSIOLOGICAL SALINE THAT LACKED CALCIUM, AND YOU CAN SEE THAT THE RESISTANCE DIDN'T CHANGE BUT SYNAPTIC RESPONSE WENT AWAY. SO THEN I WENT BACK TO NORMAL SALINE, AND THEN I PUT ON TEN MILLIMOLAR GLUTAMATES, WHICH SEEMED LIKE A LOT. AND TO MY UTMOST SURPRISE, I SAW NEITHER A CHANGE IN THE INPUT RESISTANCE, NOR A CHANGE IN THE SYNAPTIC RESPONSE. SO THAT THERE WAS NO AND THEN BACK TO NORMAL, PUT ON ASPARTATE, THESE WERE ON MUCH LONGER THAN IT TOOK TO WASH OUT THE CALCIUM AND THERE WAS NO RESPONSE. I WENT TO BOB AND I SAID, BOB, I THINK THIS MAY NOT BE CORRECT. GLUTAMATE MAY NOT BE THE NEUROTRANSMITTER TO THE AUDITORY NERVE. AS YOU MAY IMAGINE, BOB WASN'T TREMENDOUSLY HAPPY ABOUT THAT. AND MAYBE THAT'S ONE OF THE REASONS NIH WAS LUCKY ENOUGH TO GET HIM BACK, BUT I HOPE NOT. BUT BOB'S GREAT KINDNESS AND DECENCY AS HERE I WAS SORT OF CHALLENGING ONE OF HIS BIG FINDINGS, BUT INSTEAD OF BEING ANGRY WITH ME, HE JUST SORT OF WENT ABOUT HIS BUSINESS, AND PROVED ME DEAD WRONG. AND THE WAY HE DID THAT IS HE DID THAT IN WHAT THE BEST SCIENTIST WOULD DO, SO HE STARTED LOOKING AT THE GLUTAMATE RECEPTORS. FIRST, YOU KNOW, HE WAS A VIRAL CHEMIST AND LOOKED AT BINDING PROPERTIES OF TANNIC ACID RECEPTORS, WHICH ARE GLUTAMATE RECEPTORS, AND HE LOCALIZED WHERE THE GLUTAMATE RECEPTORS WERE IN THE RAT BRAINS. WHAT CLINCHED THIS, HE SHOWED AT THE INVOLVED SYNAPSES, IN THE ABC ENDS WHERE I'VE SEEN NO RESPONSES, THERE WERE AMPA TYPE GLUTAMATE RECEPTORS, SO HE PROVED ME WRONG. SO THE NEXT SET OF PAPERS THAT I LIKE VERY MUCH AND THAT OUR OWN WERE BUILT UPON IS A REAL BEAUTIFUL SET OF PAPERS ABOUT THE TRAFFICKING OF GLUTAMATE RECEPTORS. SO ONE OF MY ABSOLUTELY FAVORITE PAPERS WAS ONE THAT LONNIE AND HE PUBLISHINGED SHOWING GLUTAMATE RECEPTORS ARE SELECTIVELY TARGETED, AND TO MAKE A VERY LONG STORY VERY BRIEF, IN THE DORSAL COCHLEAR NUCLEUS, THE CELLS THAT PROJECT OUT AND GO TO THE INFERIOR CALIGULUS HAVE TWO ACTIVITIES OF DENDRITE, ONE INTO THE MOLECULAR PARALLEL FIBERS, AND IT HAS ANOTHER SET OF DENDRITES THAT DIVE INTO THE DEEP LAYER WHERE IT GETS ACOUSTIC INPUT THAT HAS NO SPINES AT ALL. THEY ARE SMOOTH DENDRITES. WHAT BOB AND LONNIE SHOWED WAS THAT THE RECEPTOR SUBUNITS IN THE APICAL TUFT WAS DIFFERENT FROM THE RECEPTOR SUBUNITS IN THE BASAL TUFT. NOW, BOB ALSO -- THIS INTEREST IN TRAFFICKING CARRIED ON INTO A NUMBER OF PAPERS, AND I'M ONLY GOING TO SHOW YOU A COUPLE HERE. HE SHOWED -- SO HE SHOWED THAT THESE RECEPTORS GO TO DIFFERENT PLACES, AND HE ALSO SHOWED THAT IN EARLY IN DEVELOPMENT, WHEN GLUTAMATE SYNAPSES HAVE MDA RECEPTORS AND THEREFORE THEY ARE SILENT, IF YOU RELEASE GLUTAMATE ONTO AN MDA RECEPTOR AT THE RESTING POTENTIAL THEY ARE MAGNESIUM BLOCKED, KEEPS THEM SHUT. AND DURING DEVELOPMENT THEN AMPA RECEPTORS ARE TRAFFICKED INTO THE SYNAPSES SO THAT SILENT SYNAPSES BEGIN TO SPEAK. ALSO, THERE'S -- THAT ACTIVITY, ACTIVATION OF NMDA RECEPTORS CONTRIBUTES TO PULLING AMPA RECEPTORS INTO THE SPINE. THAT LED US TO PUBLISH IN 2003 A PAPER I LIKED AND DON'T HAVE TIME TO GO OVER TODAY TO SHOW THAT IF WE STIMULATE THESE, APICAL DENDRITES, THE SYNAPSES ARE LPD AND HTD LIKE HIPPOCAMPAL, BUT IF WE GAVE THE SAME STIMULI TO SMOOTH BASAL DEN DRIED THERE'S NO LPD AND NO HTD, I THINK SPINES ARE VERY IMPORTANT. HIS INTEREST IN TRAFFICKING OF AMPA RECEPTORS CONTINUED TO THE VERY END OF HIS CAREER. BOB DID A LOT OF OTHER THINGS BUT I DON'T HAVE TIME TO GO OVER ALL OF HIS CONTRIBUTIONS. BUT I WANT TO SAY THAT BOB'S PAPERS SIT IN A FOLDER IN MY DESK, IT'S DOG-EARED AND HARD EVEN NOW TO READ HIS NAME ON THE LABEL. SO TODAY I WANT TO TELL YOU ABOUT A NEW SET OF EXPERIMENTS, EXPERIMENTS THAT WE'VE ONLY BEEN DOING OVER THE LAST YEAR THAT I AM REALLY THRILLED ABOUT. SO I'M GOING TO TALK ABOUT A DIFFERENT KIND OF SYNAPSE, AND IT'S NOT EXACTLY A SILENT SYNAPSE. I CALL IT A TACITURN SYNAPSE AND SHOW YOU IT'S PLASTIC. SO I'M GOING TO SHOW YOU THAT VCN HAS THREE MAJOR GROUPS OF ANATOMICALLY AND ELECTROPHYSIOLOGYICALLY DISTINCT PRINCIPAL CELLS THAT PERFORM DIFFERENT TASKS, MY FOCUS IS ON THE T STELLAT CELLS AND THEIR EXCITATORY INPUT, I'LL TELL YOU ABOUT CONNECTIONS AND HOW THEY MAY PLAY A CONTROL IN THE GENERATION OF AT LEAST SOME FORMS OF TINNITUS. HERE IS A PARASAGGITAL IN THE SAME ORIENTATION AS THE FIRST SLIDE I SHOWED YOU. HERE IS A SCHEMATIC VIEW OF THE COCHLEA, ANTERIOR TO THE RIGHT, POSTERIOR TO THE LEFT, DORSAL UPWARDS. SO HERE YOU CAN SEE WHY THE DORSAL AND VENTRICAL ARE DIFFERENT. THEY INNERVATE AND LAYERED DORSAL COCHLEAR NUCLEUS, THE PRINCIPAL CELLS, FUSIFORM CELLS, WHOSE SYNAPSES IN APICAL DENDRITE ARE PLASTIC. I'M GOING TO FOCUS ON THE UNLAYERED. SOUND IS TRANSDUCED IN THE COCHLEA, SO THAT LOW FREQUENCY SOUNDS ARE TRANSDUCED AT THE APICAL END, HIGH FREQUENCY PRODUCE U. SOUNDS ARE PRODUCED AT THE BASAL END, ON THE BASILAR MEMBRANE SHOWN HERE. HAIR CELLS TRANSMIT INFORMATION SYNAPTICALLY TO NEURONS WHOSE CELL BODIES LIE WITHIN THE CENTER OF THE COCHLEAR SPIRAL, AND THEIR AXONS TERMINATE IN THE COCHLEAR NUCLEI. THOSE AXONS THAT CARRY INFORMATION FROM THE APICAL END TERMINATE VENTRALLY, THOSE THAT CARRY INFORMATION FROM THE BASAL END TERMINATE, HERE IS LOW TO HIGH, LOW TO HIGH, AND LOW TO HIGH. NOW AUDITORY NERVE FIBERS INNERVATE AT THE PRINCIPAL CELLS, THOSE ARE RECONSIONS OF CELLS THAT WE LABELED BY PUTTING DYE INTO OUR RECORDING ELECTRODES AND YOU CAN SEE THAT THERE ARE SEVERAL DIFFERENT TYPES. YOU CAN JUST SEE FROM THEIR SHAPES. THE BUSHY CELLS HAVE THESE LITTLE SHRUBBY DENDRITES. HERE ARE TWO EXAMPLES. AND THEN THE STELLATE ARE PARALLEL TO THE PATH OF AUDITORY NERVE FIBERS, DENDRITES ARE -- SPAN THE TONOTOPIC REGION AND GET INPUT FROM ONLY A NARROW RANGE OF FREQUENCIES. HERE IS ANOTHER ONE. NOTICE HOW ITS DENDRITES ARE LINED UP PARALLEL TO AUDITORY NERVE FIBERS. AND THAT'S IN CONTRAST TO THE THIRD KIND OF PRINCIPAL CELL WHICH SPREADS DENDRITES PERPENDICULARLY. YOU CAN IMAGINE THESE CELLS RECEIVE INPUT FROM MANY AUDITORY NERVE FIBERS AND ARE THEREFORE BROADLY TUNED, BUSHY AND T STELLATE CELLS ARE NARROWLY TUNED. SO WHAT'S IMPORTANT ABOUT THIS ORGANIZATION IS THAT AUDITORY NERVE FIBERS COME ALONG AND EACH INNERVATE MULTIPLE DIFFERENT PRINCIPAL CELLS. AND IN ESSENCE, ONE PATHWAY, ONE TONOTOPIC IS SUBDIVIDED INTO MULTIPLE ASCENDING PATHWAYS, AND WHAT'S NEED ABOUT THIS ARRANGEMENT IS EACH OF THESE PATHWAYS CAN BE PERFORMING A DIFFERENT INTEGRATIVE TASK ALL SIMULTANEOUSLY. TODAY I'M GOING TO FOCUS AS I SAID ON THE STELLATE CELLS. WHAT'S INTERESTING ABOUT STELLATE CELLS? SOME OF YOU, IF YOU READ THE LITERATURE, THE TERMINOLOGY IS TERRIBLY CONFUSING. SO THEY ARE KNOWN BY LOTS OF DIFFERENT NAMES. TYPE 1 MULTI-POLAR STELLATE, T STELLATE. THIS CLASS OF STELLATE CELLS HAVE AXONS TO THE TRAPEZOID GO DORSALLY. I'M GOING TO FOCUS ON THESE T STELLATE CELLS. WHY ARE THEY INTERESTING? THEY PROJECT MORE WIDELY THAN ANY OF THE OTHER PRINCIPAL CELLS OF THE COCHLEAR NUCLEI. SO HERE ARE THE T STELLATE CELLS. HERE IS A REPRESENTATION OF THE COCHLEA, THE COCHLEA NUCLEI AND THE BRAIN. T STELLATE CELLS HAVE A BRANCH THAT PROVIDE INPUT TO THE DORSAL COCHLEAR NUCLEUS. I THINK, BUT THE EXPERIMENTS TO DO THAT ARE, WELL, IN PROGRESS, I THINK THESE T STELLATE CELLS PROVIDE MOST OF THE ACOUSTIC INPUT TO THE DORSAL COCHLEAR NUCLEUS. THEY PROVIDE INPUT TO THE NEURONS THAT PROVIDE EFFERENT FEEDBACK, BUT THEIR TARGETS HAVE NOT BEEN INVOLVED. THEY TERMINATE IN . ANOTHER THING THAT MAKES THESE T STELLATE CELLS INTERESTING THEY ARE GOOD AT ENCODINGS FEATURES THAT ARE IMPORTANT FOR UNDERSTANDING SPEECH. SO THEY ARE GOOD AT ENCODING ENVELOPE, IN THE RANGE THAT'S IMPORTANT FOR SPEECH, AND ALSO THE SPECTRUM OF SOUND. AND THEN THIRDLY, THEY ENCODE FEATURES THAT WE KNOW ARE PARTICULARLY WELL ENCODED BY COCHLEAR IMPLANTS, AND THEY FAIL TO ENCODE THOSE FEATURES THAT ARE NOT ENCODED BY COCHLEAR IMPLANTS. SO MY GUESS IS THEY ARE AN IMPORTANT PATHWAY THAT CARRIES INFORMATION IN COCHLEAR IMPLANT USERS. SO THESE T STELLATE CELLS RESPOND TO SOUND AS CHOPPERS, AND BASICALLY ALL THAT MEANS IS THAT THEY GO BRRRRRR IN RESPONSE TO A TONE. THEY FIRE VERY REGULARLY. AND IF YOU PRESENT A WHOLE BUNCH OF THESE SOUNDS, AS BILL AND PHIL DID HERE, 200 PRESENTATIONS, AND SHOWING WHEN THE SPIKE OCCURS, AND IF YOU DO A HISTOGRAM YOU SEE THIS PATTERN OF MODES WHICH IS WHAT GIVES THEM THE CHOPPER NAME, AND THERE'S NOTHING MAGIC ABOUT THIS EXCEPT THAT THE FIRST SPIKED LINE UP REALLY WELL, THE NEXT ONES HAVE MORE JITTER AND LINE UP A LITTLE LESS WELL, UNTIL THE CHOPPING PATTERN DISAPPEARS. BUT BASICALLY THESE NEURONS ARE JUST FIRING REGULARLY. BRRRRR, EVERY TIME ENERGY GOES INTO THE RECEPTIVE FIELDS. ANOTHER THING THAT'S ACTUALLY QUITE REMARKABLE IS THAT IF YOU LOOK AT THE FIRING RATES AS THEY RESPOND TO A TONE OF SOMETHING LIKE 25 MILLISECONDS, IT'S THAT THEIR FIRING RATE IS AMAZINGLY CONSTANT, AND THAT'S SURPRISING BECAUSE THEIR AUDITORY NERVE INPUTS ARE ADAPTING, FAST FIRST AND AN IMPORTANT FEATURE OF THESE IS THAT THE PERIOD OF THIS FIRING IS UNRELATED TO SOUND. SO THIS PERIOD CARRIES NO INFORMATION ABOUT FINE SO T STELLATE CELLS ALSO HAVE INHIBITOR SIDE BANDS, SO AGAIN THIS IS FROM AN OLD PAPER, WHICH CAUSES -- BILL AND STEVE GREENBERG CAUSED CELLS TO FIRE BY GIVING BACKGROUND NOISE AND THEN YOU CAN SEE THAT THEY HAVE INHIBITOR SIDE BANDS WHICH MAKES THEM ESPECIALLY GOOD AT ENCODING SPECTAL PEAK. AND NOTICE THAT IF YOU LOOK AT THE FIRING RATE OF FUNCTION OF INTENSITY, THE FIRING RATE INCREASES MONOTONICALLY WITH INTENSITY I TELL YOU ALL THAT BECAUSE THESE FEATURES ACCOUNT FOR WHY THEY ARE SO GOOD AT ENCODING SPECTRUM. SO HERE IS ANOTHER -- RESULTS FROM ANOTHER OLD PAPER WHERE BLACKBURN AND SACHS PRESENTED THE VOWEL TO NEURONS INCLUDING HOPPERS, AND SHOWED THAT CHOPPERS ENCODE THE PERFORMANCE OF THE VOWEL "E" OVER VERY WIDE RANGE OF INTENSITY, SO THIS LED SACHS TO THINK THAT CHOPPERS, THE ROLE OF CHOPPERS, IS TO ENCODE SPECTRUM, AND ALL OF US CAN UNDERSTAND WHY SPECTRUM IS IMPORTANT FOR UNDERS SPEECH, AND FOR LOCALIZING SOUNDS. SO NOW I'M GOING TO TALK ABOUT OUR OWN EXPERIMENTS IN SLICES. SO HERE IS WHAT T STELLATE CELLS DO IF WE INJECT CURRENT, HERE UP AND DOWN, AND NOTICE THIS T STELLATE CELL HAS A RESTING POTENTIAL, AND THEN FIRES MORE AND FIRES LESS, AND LOOK AT HOW BEAUTIFULLY THE FIRING RATE REFLECTS THE CURRENT THAT DEPOLARIZED THE CELL. IN RESPONSE TO STUDY DEPOLARIZATION, THIS CELL DOES WHAT T STELLATE CELLS LOVE TO DO, GO BRRRRRR, THEY FIRE VERY REGULARLY. SO AS I'VE SAID BEFORE, JUST THE ANATOMY TELLS YOU THESE CELLS PROBABLY GET INPUTS FROM RELATIVELY FEW AUDITORY NERVE FIBERS, AND WE'RE ABLE TO SHOW PHYSIOLOGICALLY BY RECORDING WITH THE SHARP ELECTRODE FROM A T STELLATE CELL AND STIMULATING AUDITORY NERVE FIBERS AND THEN GRADUALLY CRANKING UP THE VOLTAGE. SO HERE YOU CAN SEE -- HERE WE MADE THE SHOCK, AND THEN AS THE VOLTAGE -- STIMULATING VOLTAGE INJECTED CREASED WE GET EPSD THAT GROWS AND GROWS AND GROWS. IF WE PLOT, WE CAN SEE THE CELL IS GETTING INPUT FROM ONE, TWO, THREE, FOUR, FIVE AUDITORY NERVE FIBERS. WHICH IS WHY THEY ARE NEVER REALLY TUNED BUT THOSE AREN'T THE ONLY INPUTS TO T STELLATE CELLS. WAY BACK, WHEN WE FIRST LOOKED AT THE ANATOMY OF THESE CELLS, WE NOTICED THAT THEIR DENDRITES SHOWN HERE IN BLACK LIE LINED UP IN AN ISOFREQUENCY LAMINA, AND IN THE SAME ISOFREQUENCE LAMINA THE AXON HAS LOCAL COLLATERAL ENDINGS. HERE IS ANOTHER ONE. HERE ARE THE DENDRITES. HERE ARE THE COLLATERAL ENDINGS, WHICH ARE JUST LINED UP IN THE SAME ISOFREQUENCY LAMINA. SO BECAUSE IN THIS AREA OF THE POSTERIOR VENTRAL COCHLEAR NUCLEUS, IT'S THOUGHT THE TAR GETS OF THESE TERMINALS ARE OTHER T STELLATE CELLS. SO WE DECIDED TO TEST THAT ELECTROPHYSIOLOGICALLY. SO WE ACTUALLY WENT TO MY SON'S LAB, BARRY CONOR'S LAB, AND MY SON TAUGHT MY COLLEAGUE AND ME TO DO DUAL RECORDINGS. AND WE STARTED LOOKING AT THE SYNAPTIC CONNECTIONS BETWEEN THEM. SO WE IMAGINED THAT SCHEMATICALLY T STELLATE CELLS WOULD BE CONNECTING TO ONE ANOTHER WITHIN AN ISOFREQUENCY LAMINA LIKE THAT. SO WE STARTED TO MAKE RECORDINGS FROM PAIRS, SHE RECORDED FROM ONE T STELLATE CELL IN CLAMPS, WE LOOKED FOR CONNECTIONS. THE FIRST ONES WE SAW WERE WEIRD. IN FACT SLIGHTLY RIDICULOUS. SO HERE SHE CAUSED THE BLACK CELL TO FIRE LOTS OF ACTION POTENTIALS, AND THE POST-SYNAPTIC CELL HERE FIRED WITH ONLY A FEW ACTION POTENTIALS. MOST WEREN'T DOING ANYTHING. AND IN FACT HERE IS ANOTHER ONE WITH A LITTLE BIT LESS CURRENT FIRED MORE SLOWLY, AND NOTHING HAPPENED AT ALL. IN FACT, THESE CONNECTIONS -- SHE DIDN'T SEE THAT OFTEN. OF THE FIRST 23 PAIRS, ONLY FIVE SHOWED THESE VERY WEAK OR TACITURN CONNECTIONS. SO THAT MADE ME THINK OF SILENT SYNAPSES, THE SILENT SYNAPSES I TOLD YOU BEFORE BOB WENTHOLD LOOKED AT, AND OTHER PEOPLE LOOKED AT IN THE CORTEX. SO CAO RECORDEDDED FROM A PAIR, ONE IN CURRENT CLAMP, THE OTHER IN VOLT CLAMP, THIS SYNAPSE WAS SILENT. SO THEN JUST LIKE IN THE HIPPOCAMPUS, SHE PAIRED PRESYNAPTIC FIRINGS WITH POST-SYNAPTIC DEPOLARIZATION TO 30 MILIVOLTS AND LEFT IT THERE FOR 1.2 SECONDSES, AND SHE SAW THAT SHE COULD SEE THESE LITTLE REVERSE EPSCs, POTENTIATED MORE, AND THEN TOOK THE VOLTAGE BACK DOWN TO -65, THE SYNAPSE WHICH WAS SILENT BEGINS TO SPEAK, BUT IT'S STILL PRETTY WIMPY BECAUSE NOT NEARLY EVERY ACTION POTENTIAL IS GIVING AN EPSC, AND THESE ARE ALL ROUGHLY THE SAME SIZE. WHEN WE COMPARED THE SHAPES OF THESE TWO EPSCs, WE -- THESE ARE SHOWN AS LARGER SCALE HERE, YOU CAN SEE THAT THE SHAPES ARE NOT SO DIFFERENT. ACTUALLY WE WONDERED WHETHER WE COULD SEE NMDA COMPONENTS THAT WERE SLOWER, BUT WE DIDN'T SEE THAT. ON THE OTHER HAND THAT COULD BE A VOLTAGE ARTIFACT. FURTHER POTENTIATION RESULTED IN AN INCREASE IN THE NUMBER OF THESE EPSCs BUT NOTICE THE AMPLITUDE IS NOT GROWING. SO A SUMMARY OF THIS EXPERIMENT IS SHOWN HERE, WHERE THE CELLS STARTED SILENT, POTENTIATION CAUSED THE CELLS TO SPEAK AND THEN THAT POTENTIATION FADED AWAY IN MINUTES AND THEN LONGER POTENTIATION INCREASED FREQUENCY AND DURATION. NOW I WANT TO EMPHASIZE THAT IN THE HIPPOCAMPUS AND CORTEX WHEN ONE TALKS ABOUT LTP, IT'S THE AMPLITUDE OF EPSCs THAT CHANGES. AND THE AMPLITUDE OF EPSCs RESULTS FROM THE RECRUITMENT OF AMPA RECEPTORS BOB HAD STUDIED. WHAT WE'RE SHOWING HERE IS THAT IT'S THE PROBABILITY OF A CURRENT OF EPSCs THAT'S CHANGING, HERE AND HERE, NOT THE AMPLITUDE. AND THAT'S A PRESYNAPTIC FUNCTION. THE FACT THAT A POST -- SO BEFORE I SPEAK ABOUT NITRIC OXIDE LET ME SHOW YOU ANOTHER PROPERTY. NOT NEARLY EVERY SPIKE GIVES AN EPSC, SO HERE IS AN EXAMPLE OF A PAIR THAT'S VERY HEAVILY POTENTIATED, WHERE THERE ARE LOTS OF EPSCs, BUT NOTICE IT'S AS IF THESE TWO CELLS ARE OSCILLATING BUT THEY ARE NOT OSCILLATING AT EXACTLY THE SAME FREQUENCY. AND IF WE LINE UP THE PRESYNAPTIC SPIKES WITH THE POST-SYNAPTIC RESPONSES THEY ARE ALL OVER THE PLACE. AND THAT SUGGESTION THAT THE CONNECTION THAT WE'RE LOOKING AT IS NOT A ONE-TO-ONE CONNECTION. AND SO I'VE MODIFIED MY WORKING HYPOTHESIS DIAGRAM HERE, AND SHOWN HERE A PRESYNAPTIC CELL, HERE POST-SYNAPTIC, WE THINK THERE'S AN INTERNEURON IN BETWEEN. WE THINK THIS IS LIKELY TO BE A T STELLATE CELL, BUT WE HAVE NOT YET PROVEN IT. NOW BACK TO NITRIC OXIDE SIGNALING, SO FROM A REVIEW PAPER THERE'S SNYDER AND COLLEAGUE GAVE THIS NICE SUMMARY DIAGRAM THAT VERY OFTEN NITRIC OXIDE WORKS IN NEURONS, LIKE THIS, THAT NMDA RECEPTORS OPEN, ALLOW CALCIUM TO COME IN, CALCIUM CALMODULIN ACTIVATES SYNTHASE CAUSING PRODUCTION OF NITRIC OXIDE, THEY REACTIVE GAS, THAT DOES ALL KINDS OF THINGS INCLUDING SPREADING BACKWARDS ACROSS THE SYNAPSE AND ACTIVATING SOLUBLE GLYCOLACE. WELL, IT TURNS OUT ALL OF THESE ELEMENTS ARE PRESENT IN T STELLATE CELLS, THERE'S A LOVELY PAPER IN 2001 WHICH SHOWS PICTURES, NOW THESE ARE CORONAL SECTIONS, LATERAL, MEDIAL, DORSAL AND VENTRAL, THE AUTHORS CHOSE TO ILLUSTRATE WHERE THERE ARE MOST T STELLATE CELLS. I'M GOING TO BE MOBILE AGAIN. THANK YOU. THAT'S MUCH NICER TO BE MOBILE. SO THEY SHOWED THAT PART OF THE COCHLEAR NUCLEI HAS NEURONAL NITRIC OXIDE SYNTHASE, AND THOSE ARE IN THE SAME CELLS AND IN FACT HERE IS A TRIPLE LABEL, AND THEY ARE ALL IN THE SAME CELLS, WHICH IS WHAT WE WOULD BE EXPECTING IF THERE'S NITRIC OXIDE SIGNALING IN CONNECTIONS BETWEEN T STELLATE CELLS. SO WE TESTED THAT HYPOTHESIS. SO FIRST WE BLOCKED NITRIC OXIDE SYNTHASE AND SO CIO MADE RECORDING, PRESYNAPTIC AND CURRENT CLAMP, POST-SYNAPTIC IN VOLT CLAMP AND TESTED WHETHER THE COMPOUND L-NAME WOULD BLOCK EPSCs AND THEY D FIRST PRESYNAPTIC CELL WAS FIRING AT 33 PER SECOND, NO RESPONSE, THEN SHE DID THE PAIRING OF POST-SYNAPTIC DEPOLARIZATION AND PRESYNAPTIC FIRING AND HERE YOU SEE THESE EPSCs APPEARING, AND THEN AFTER THAT FADED AWAY SHE PUT ON L-NAME, AND DID THE PAIRING AND NOW LOOK, NOTHING HAPPENS. IN FACT, EVEN AT THE VERY END OF THAT RECORDING NOTHING HAPPENED. SO NITRIC -- SO THE BLOCKING OF NITRIC OXIDE SYNTHASE SEEMS TO BLOCK THEY CONNECTION. SO ANOTHER EXPERIMENT THAT WE COULD DO WAS TO BLOCK THE NMDA RECEPTORS WITH EPV, SAME EXPERIMENTAL SETUP, AND APV BLOCKS THE EPSCs, AGAIN THIS CELL FIRING 20 PER SECOND, THE C CELL SHOWED NO RESPONSE, THEN SHE DID THE POTENTIATION AND THERE COME EPSCs WHICH THEN FADE AWAY, AND NOW AFTER THAT SHE PUT ON APV, AND THIS AND THAT POTENTIATION YIELDED NOTHING AT ALL. SHE KEPT THIS FOR 45 MINUTES AND WAS ABLE TO GET POTENTIATION BACK AGAIN. ANOTHER THING WE WOULD EXPECT IF WE PUT ON A NITRIC OXIDE DONOR INTO THE BATH WE WOULD EXPECT ALSO TO SEE A RESPONSE. SO CIO RECORDED FROM A T STELLATE CELL, FROM AN OCTOPUS CELL SIMULTANEOUSLY WHICH DID NOTHING SO I DIDN'T SHOW IT, BUT HERE IS UNDER CONTROL CONDITIONS, IN THE PRESENCE OF THE NITRIC OXIDE DONOR SAW ALL THESE EPSCs, AFTER 1 1/2 HOURS THEY WERE GONE. SO THESE EPSC -- I'VE SHOWN YOU THAT T STELLATE CELLS HAVE THESE POTENTIATED EPSCs, THE DONOR EPSCs, AND YOU CAN COMPARE THE SHAPES HERE, THIS IS THE VERY LARGEST ONE WE RECORDED, AND HERE FOR COMPARISON I'VE SHOWN THE RESPONSE TO A SHOCK OF AUDITORY NERVE FIBERS IN T STELLATE CELLS, THE SHAPE IS NOT EXACTLY THE SAME BUT THEY ARE ALL GLUTEMATERGIC. WE SHOWED YEARS AGO THE EPSPs IN T STELLATE CELLS HAVE BOTH NMDA COMPONENT, THE SLOW RESPONSE TO SHOCK WHICH IS GIVEN, AND IF WE ADD A BLOCKER OF AMPA RECEPTORS THE WHOLE RESPONSE IS GONE AND IT'S REVERSIBLE. SO THESE EPSCs THAT ARE PRODUCED BY POTENTIATION ARE SENSE ACTIVE TO DNQX, AS THOSE ARE PRODUCED BY NITRIC OXIDE DONORS. SO THEN COMES THE QUESTION, WHETHER THESE CONNECTIONS ARE UNIDIRECTIONAL OR BIDIRECTIONAL. SO WE TESTED THAT DIRECTLY, SO AT FIRST CIO MADE THIS NEURON ONE, THE BLACK NEURON, PRESYNAPTIC AND LOOKED AT NEURON TWO, AND THEN SWITCHED THEM, SO NOTICE HERE THE PRESYNAPTIC NEURON IS FIRING AWAY, THERE'S A RESPONSE IN THE POST-SYNAPTIC TURN, WHEN SHE PUT IT IN THE OPPOSITE DIRECTION THERE ARE ALSO EPSCs. SO THAT TELLS US THESE CONNECTIONS BETWEEN T STELLATE CELLS ARE BIDIRECTIONAL, NOW YOU'LL SEE I ADDED SOME MORE LITTLE HYPOTHETICAL SYNAPSES. SO WHAT'S INTERESTING ABOUT THIS IS THAT IF WE HAVE BIDIRECTIONAL GLUTAMTERGIC EXCITABLE SYNAPSES THEY CAN MAKE FEEDBACK LOOPS, LIKE THIS, LIKE THAT, AND THAT MAKES IT ALMOST IMPOSSIBLE NOT TO THINK ABOUT TINNITUS. SO THINKING ABOUT THAT, THEN LEADS TO THE QUESTION WHETHER TINNITUS AND NITRIC OXIDE ARE AT ALL CONNECTED. SO ACTUALLY WHEN I WAS TELLING MY HUSBAND THIS, HE IMMEDIATELY WENT TO THE INTERNET, AND FOUND THAT THE FDA GIVES WARNINGS TO MEN WHO TAKE VIAGRA AND ONE OF THE WARNINGS IS THAT 34% OF MEN WHO TAKE VIAGRA COMPLAIN OF RINGING IN THE EARS. SO NITRIC OXIDE AND TINNITUS ARE ASSOCIATED AS WE MIGHT EXPECT. NOW IN THE LITERATURE, THERE ARE REALLY SOME HINTS THAT THIS MIGHT INDEED BE THE CASE. A LOVELY PAPER BY ERIC YOUNG AND SOME OF HIS COLLEAGUES LOOKED AT CATS WHO WERE EXPOSED TO NOISE TRAUMA, AND THEN RECORDED FROM CHOPPERS, AND WHICH ARE T STELLATE CELLS, AND PRIMARY THAT ARE BUSHY CELLS, AND HERE IS WHAT THEY FOUND. SO IN THE NORMAL CHOPPERS, NOTICE THAT THE THRESHOLDS ARE NICE AND LOW, SO HERE IS LEVEL, HERE IS THE DRIVEN RATE IN ACTION POTENTIAL FOR SECONDS, AND SO AT VERY LOW LEVELS THE CHOPPERS START TO FIRE AND THEN THEY ARE FIRING LEVELS OFF. IN NOISE EXPOSED CHOPPERS, THE THRESHOLDS ARE HIGHER, BUT THEN LOOK AT WHAT HAPPENS TO THE FIRING RATES. THEY GO THROUGH THE ROOF. AND CONTRAST THAT WITH WHAT HAPPENS IN BUSHY CELLS. THERE UNDER NORMAL BUSHY CELLS HAVE LOW THRESH HOLDS, THE FIRING RATE INCREASES, BUT IN THE NOISE EXPOSED ONES THE THRESHOLDS ARE HIGHER AND FIRING RATE IS LOWER THAN IN THE NORMAL ONES. THE FIRING RATE AS A FUNCTION OF LEVELS IS ACTUALLY REVERSED BY NOISE TRAUMA. ANOTHER PIECE OF EVIDENCE THAT FROM A PAPER BY COOMBER ET AL. PUBLISHED RECENTLY AND LOOKS AT NITRIC OXIDE SIGNALING AND AGAIN THEY HAPPEN TO ILLUSTRATE THE PVCN, THAT AREA THAT HAS LOST T STELLATE CELLS. THEY TOOK GUINEA PIGS, EXPOSED TO NOISE ON ONE SIDE, NOT ON THE OTHER. AND NOTICE IN THE -- OH, I SHOULD EXPLAIN THAT NADPH DIAPHORASE REVEALED NITRIC OXED SENSITIVITY. ON THE TRAUMATIZED SIDE THIS DIAPHORASE ACTIVITY IS MUCH GREATER THAN ON THE CONTROL SIDE. AND HERE IS IMMUNOHISTOCHEMISTRY TO SHOW NITRIC OXIDE SIN THIS IS AND NADPH DIAPHORASE ACTIVITY. IT LOOKS AS IF TRAUMA IS ACTUALLY INCREASING THE STRENGTH OF NITRIC OXIDE SIGNALING. SO ANOTHER THING THAT'S REALLY STRIKING IS THAT A LOT OF THE TARGETS OF T STELLATE CELLS HAVE BEEN ASSOCIATED WITH HYPER EXCITABILITY WITH TINNITUS. SO I TOLD YOU THAT T STELLATE CELLS INNERVATE DORSAL COCHLEAR NUCLEUS AND I THINK PROVIDE MAJOR ACOUSTICAL INPUT. IT WAS ONE OF THE FIRST PLACES WHERE PEOPLE THOUGHT THERE WAS HYPERACTIVITY IN THE PRESENCE OF TINNITUS. THERE'S ALSO -- BY THE WAY HERE I'VE DOCUMENTED WHAT THE -- WHO SHOWED THERE WERE PROJECTIONS AND WHO WHO SHOWED HYPERACTIVITY, A LOT OF WORK DONE BY JIM. MORE RECENTLY SHOWN THE VNTB WHOSE PROJECTIONS ARE FROM T STELLATE CELLS ARE HYPER-EXCITABLE IN THE PRESENCE OF TINNITUS, ALSO THE INFERIOR CALIGULUS IS THE TARGET OF ALL KIND OF THINGS, THERE'S HYPER EXCITABILITY THERE, IN THE AUDITORY CORTEX, AND NOBODY HAS LOOKED IN THE THALAMUS. SO IT'S STRIKING A LOT OF THE TARGETS OF T STELLATE CELLS ARE HYPER EXCITABLE WITH TINNITUS. LET ME TELL WHAT YOU OUR CONCLUSIONS ARE. SO I'VE SHOWN YOU THAT T STELLATE CELLS ARE BIDIRECTIONALLY INTERCONNECTED. THAT THE INTERCONNECTIONS ARE TACITURN, THEY DON'T DO MUCH, THEY HAVE TO BE POTENTIATED. THE INTERCONNECTIONS ARE POTENTIATED BY PAIRING POST-SYNAPTIC DEPOLARIZATION WITH PRESYNAPTIC FIRING, THE INTERCONNECTIONS IN OUR RECORDINGS ARE POLY SYNAPTIC, I DON'T KNOW THESE ARE INTERMEDIARY NEURONS BUT I THINK THEY PROBABLY ARE. POTENTIATION REQUIRES RETROGRADE SIGNALING, THAT SIGNALING IS LIKELY BY NITRIC OXIDE. AND WHAT'S IMPORTANT IS THAT THESE INTERCONNECTIONS ARE BIDIRECTIONAL AND CAN FORM POSITIVE FEEDBACK LOOPS, AND THESE INTERCONNECTIONS WITH CONTRIBUTE TO TINNITUS. AND LET ME JUST STOP HERE FOR ONE MOMENT AND SAY SOMETHING SO IMAGINE NOW TINNITUS IS SOMETHING PEOPLE GET AFTER AUDITORY NERVE FIBERS ARE AFFECTED BY NOISE TRAUMA. THEY EITHER CHANGE THEIR ACTIVITY OR THEY DEGENERATE COMPLETELY. SO THESE NEURONS, YOU CAN IMAGINE, IF NOW THESE INPUTS DEGENERATE, IT'S VERY LIKELY BECAUSE NEURONS TEND TO HAVE HOMEOSTATIC PLASTICITY AT THE THEY LIKE TO BE ACTIVATED TO CERTAIN LEVELS THAT THESE CONNECTIONS BECOME STRONGER, AND SO THESE INTERCONNECTIONS MAY BECOME STRONGER AND WE KNOW THAT THE NITRIC OXIDE SIGNALING ALSO BECOMES STRONGER, IN THE PRESENCE OF DEGENERATION OF THEIR INPUT. WE KNOW VIAGRA CAUSES RINGING OF THE EARS. THE CHOPPERS ARE HYPER EXCITABLE AFTER NOISE TRAUMA. NITRIC OXIDE SIGNALING STRENGTHENS AFTER NOISE TRAUMA. AND THAT THE TARGETS OF T STELLATE CELLS VE BEEN SHOWN TO BE HYPEREXCITABLE. SO I WOULD LIKE TO THANK THE COLLEAGUES WHO DID THIS WORK, AND MOST IMPORTANT CIO AND I WENT TO BARRY CONOR'S, WORKED WITH MY SON, DID DUAL RECORDINGS, ESSENTIAL FOR ALL THAT WE DID. AND THEN THE PEOPLE AND HERE IS MY SON. AND OTHER COLLEAGUES HAVE WORKED WITH ME AND HAVE DONE THE WORK THAT LED UP TO THESE IDEAS. LET ME END WITH THIS PICTURE FROM NEW ZEALAND, WHERE GARY HOUSELY ORGANIZED THIS MEETING, BOB AND I BOTH WERE THERE. A PARTICULARLY LOVELY PART OF THE TRIP WAS WE WERE TAKEN FROM AUCKLAND TO AN ISLAND CALLED TRI TRI MATANGI ISLAND, RESTORED WITH NATIVE NEW ZEALAND PLANTS BY SCHOOL CHILDREN WHO CAME IN GROUPS TO HELP PLANTS, IN FACT PLANTS GROWN BY THE LIGHTHOUSE KEEPER WHO LIVED ON THIS ISLAND, AND SO THEY WERE RESTORING NOT ONLY THE PLANTS BUT THEY ALLOWED BIRDS THAT NEST ON THE GROUND TO SURVIVE BECAUSE IT TURNED OUT THAT WHEN PEOPLE CAME WITH SHIPS AND RATS, THE RATS WOULD EAT ALL THESE EGGS, SO THIS ISLAND WAS A BIRD REFUGE AS WELL AS A BEAUTIFUL PLANT RESTORATION PROJECT. AND SO HERE YOU SEE BOB AND GARY HOUSELY, AND THERE'S BOB, THERE'S ME, IN THIS LOVELY TIME. AND SO LET ME THANK YOU FOR THE GREAT HONOR AND THANK YOU TO THE FAMILY FOR BEING HERE. I WON'T TELL YOU HOW MUCH I LIKE AND RESPECT BOB, HOW LUCKY I WAS TO HAVE HAD HIM AS A COLLEAGUE. THANK YOU. [APPLAUSE] >> WE HAVE TIME FOR QUESTIONS. >> IS IT POSSIBLE TO MAKE -- (INAUDIBLE). >> IT'S VERY DIFFICULT, AND IN FACT I EVEN WANT TO AVOID THE QUAGMIRE OF HAVING TO PROVE THAT AN ANIMAL HAS TINNITUS. IT TURNS OUT THAT BEHAVIORALLY THAT'S EXTREMELY DIFFICULT, AND I JUST WANT TO GET AWAY FROM IT. WHAT OUR PLANS ARE IS THAT WE PLAN TO CAUSE TYPE 1 AUDITORY NERVE FIBERS TO DEGENERATE BY JUST APPLYING WEBBING TO THE MIDDLE EAR, HAVING THEM DEGENERATE AND LOOK TO SEE WHAT HAPPENS TO THE T STELLATE CELL CONNECTIONS AS A FUNCTION OF REMOVING THEIR INPUTS, AND NOT WORRYING ABOUT TINNITUS FOR THE MOMENT. YEP. >> SO AT FIRST GLANCE THE EXPERIMENTS SHOW -- (INAUDIBLE) >> BUT WITH A DIFFERENCE THAT IT'S NOT AMPLITUDE THAT CHANGES FRY, IT'S EPSCs. >> BUT THEY SHOW -- (INAUDIBLE). >> THAT MANY EPSC GROWS IN AMPLITUDE. >> WELL, NOT IN SINGLE SYNAPSES (INAUDIBLE) >> IN FACT NITRIC OXIDE HAS-SHOWN TO AFFECT IH CURRENT, T STELLATE CELLS HAVE IH CURRENT, SO YOU'RE RIGHT ABOUT THAT, BUT IT WAS STRIKING HOW ALL OF THESE TOOLS FOR NITRIC OXIDE PREVENTED THE POTENTIATION IN OUR HANDS, YEAH. >> (INAUDIBLE). >> WE ONLY DISCOVERED THIS A YEAR-AND-A-HALF AGO, SO THERE ARE MANY THINGS I DON'T KNOW. AND I AGREE, THIS IS NOT A FINISHED STORY. IN FACT, ALL OF WHAT YOU'VE HEARD IS COMPLETELY UNPUBLISHED. YEAH. >> SO YOU MENTIONED -- (INAUDIBLE). >> WE HAVE NEVER SEEN ANY GAP JUNCTION COUPLING IN THE END OF THESE AT ALL. ACTUALLY ANATOMICALLY, LONNIE SUGGESTED THAT BUSHY CELLS ARE COUPLED, SO HE SAW WHAT HE THOUGHT WERE GAP JUNCTIONS BUT PHYSIOLOGICALLY WE'VE NEVER SEEN HIDE NOR HAIR AND DON'T KNOW OF GAP JUNCTION COUPLING. YES? >> (INAUDIBLE). >> THAT'S ACTUALLY WHY I POINTED OUT TO YOU THAT THE FIRING RATE OF CHOPPERS IS CONSTANT. ESPECIALLY THE SUSTAINED CHOPPERS. AND THAT SEEMS TO ME TO BE A PARTICULARLY USEFUL FEATURE FOR NEURONS THAT ENCODE SPECTRUM BECAUSE IT MEANS THAT IF YOU HAVE THIS TONO TOPICALLY ORGANIZED POPULATION YOU DON'T ALSO HAVE A CHANGE IN TIME, SO IF A CELL IS ADAPTING THEN YOUR MAP OF SPECTRUM WOULD BE CHANGING WITH TIME. AND IT MAY BE THAT THIS POSITIVE FEEDBACK IS JUST SORT OF FILLING IN FOR THE ADAPTATION. BUT THAT'S SPECULATION. BUT THERE'S NO DOUBT IN MY MIND THAT IT PLAYS A ROLE IN NORMAL HEARING. >> (INAUDIBLE). >> OH, IN FACT I SHOWED YOU THAT THEY HAVE INHIBITORY SIDE BANDS AND DIDN'T HAVE TIME TO TELL YOU THAT THE D STELLATE CELL CELLS ARE THE SOURCE OF THE INHIBITORS SIDE BANDS, IN THESE THE GLYCOMERGIC BANDS CROSS TO THE OTHER SIDE OF THE COCHLEA NUCLEUS AND PROVIDE INHIBITION IPSI AND CONTRA LATERALLY, DEFINITELY THEY HAVE INHIBITION. YES, JONATHAN? >> (INAUDIBLE). >> NITRIC OXIDE. >> (INAUDIBLE). >> NOBODY'S TESTED THAT, WE HAVEN'T LOOKED AT IT IN VIVO. THANK YOU FOR YOUR WONDERFUL ATTENTION. [APPLAUSE]